I buy a lot of laptops through Ebay. The one problem which occurs time after time is damage in transit. Over the last few months I have bought at least 20 laptops and I have had 4 of these damaged in transit. The common factors were as follows.
1. All of them had been sent by Royal Mail.
2. All of them were sent wrapped and bagged (not boxed).
3. All of them had insufficient padding around them.
Please, if you must use Royal Mail to send laptops then put them in a box with lots of padding around them. Too often sellers are charging £20-25 for postage then wrapping it in newspaper and brown tape and posting it by parcel post (costing about a tenner). Why rip people off and risk negative feedback to save a couple of quid on postage? Personally, I would rather pay an extra few pounds for postage and know it was going to be in 1 piece when it arrives.
Finally, you can get a much better service from a courier. For laptops they are cheaper, faster and better insured than Royal Mail. You do not have to be a trader to use a courier company. In my opinion the best is CityLink. (check out their website). I can send any parcel up to 10kg (more than enough for a boxed laptop) anywhere in the UK for only £7.95. Delivery is signed for next day and your goods are fully insured by a company who care about delivering a service.